Soil contamination by petroleum hydrocarbon compounds continues to be a common occurrence, with such contamination occurring both naturally and from, for example, storage tanks. Unfortunately, the cleanup of such contamination is both costly and can be potentially hazardous to those performing the cleanup. Typically, unless the contamination exposes immediate harm to human and ecological health, remediation methods that result in the least land alteration are usually preferred.
In situ bioremediation is often a cost-effective and non-intrusive method for treating petroleum hydrocarbon-contaminated soils and has been utilized for decades. To enhance in situ bioremediation, typical measures include bioaugmentation with certain microbial species and stimulating indigenous microorganisms by injecting amendments that have been depleted in the contaminated matrices. For complete biodegradation of organic contaminants, the availability of terminal electron acceptors (e.g., O2, NO3—, SO42−) is usually important. For example, to enhance aerobic degradation of contaminants, air is usually sparged to replenish O2 that is depleted. Unfortunately, the addition of oxygen releasing compounds or alternative electron acceptors can be energy and cost intensive.
Compared with external electron acceptor supplement, bioelectrochemical systems (BESs), such as microbial fuel cells (MFCs), have recently been studied as alternatives to enhance biodegradation of petroleum hydrocarbons. For example, electrochemically active bacteria (EAB) on the anode of an MFC can catalyze the oxidization of organic electron donors such as hydrocarbon and extracellularly transfer electrons to the anode. Electrons are then transferred through an external circuit to a cathode, where typically O2 is reduced to H2O.
Attention for the application of BES for remediation of contaminated soil, groundwater, and sediment has increased in industry. However, the performance of presently known systems is limited by distances from the electrode and/or low water content in the soil and/or medium to be remediated. Accordingly, there exists a need in the art for BESs that can maximize the radius of influence (ROI) from the electrode(s), effectively operate in vadose zone conditions, generate at least enough power in order to make the monitoring of the system self-sufficient, and/or use cost-effective materials for their construction.
The present application provides new technology that will greatly improve groundwater and soil remediation efficiency and reduce costs over a range of different moisture levels and soil compositions, as well as provide effective remediation for a variety of contaminant types.
One aspect of the present application relates to a method for the remediation of a substrate comprising at least one contaminant. The method comprises: contacting a substrate comprising at least one contaminant with a bioelectrochemical system comprising: at least one BES column comprising a central tube having one end open to the an oxygen-containing gaseous environment and a perforated opposite end configured for submersion into substrate; a cathode layer external to said central tube configured for encasing at least a portion of the perforated portion of said central tube; a separator layer external to said cathode layer, wherein said separator layer isolates said cathode layer from substrate; an anode layer external to said separator layer, wherein said separator layer isolates said anode layer from said cathode layer; a containment layer external to said anode layer; and an electrical current interface functionally connecting said anode layer to said cathode layer. The system is then operated to reduce the amount of the at least one contaminant in said substrate.
Another aspect of the present application relates to a method for the generation of electricity via bioelectrochemical reaction. The method comprises contacting a substrate comprising at least one contaminant with a bioelectrochemical system comprising: at least one BES column comprising a central tube having one end open to the an oxygen-containing gaseous environment and a perforated opposite end configured for submersion into substrate; a cathode layer external to said central tube configured for encasing at least a portion of the perforated portion of said central tube; a separator layer external to said cathode layer, wherein said separator layer isolates said cathode layer from substrate; an anode layer external to said separator layer, wherein said separator layer isolates said anode layer from said cathode layer; a containment layer external to said anode layer; and an electrical current interface functionally connecting said anode layer to said cathode layer. The system is then operated to generate electricity.